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Biomedical subjects

C H Kim

Publications and source records attributed to C H Kim.

At least 307 records · Page 17Linked to original sources
PubMed1995

Characterization and substrate specificity of an endo-beta-1,4-D-glucanase I (Avicelase I) from an extracellular multienzyme complex of Bacillus circulans.

An endo-1,4-beta-D-glucanase I (Avicelase I; EC 3.2.1.4) was purified to homogeneity from an extracellular celluloxylanosome of Bacillus circulans F-2. The purification in the presence of 6 M urea yielded homogeneous enzyme. The enzyme had a monomeric structure, its relative molecular mass being 75 kDa as determined by gel filtration and 82 kDa as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The pI was 5.4, and the N-terminal amino acid sequence was ASNIGGWVGGNESGFEFG. The optimal pH was 4.5, and the enzyme was stable at pH 4 to 10. The enzyme has a temperature optimum of 50 degrees C, it was stable at 55 degrees C for 46 h, and it retains approximately 20% of its activity after 30 min at 80 degrees C. It showed high-level activity towards carboxymethyl cellulose (CMC) as well as p-nitrophenyl-beta-D-cellobioside, 4-methylumbelliferyl cellobioside, xylan, Avicel, filter paper, and some cello-oligosaccharides. Km values for birch xylan, CMC, and Avicel were 4.8, 7.2, and 87.0 mg/ml, respectively, while Vmax values were 256, 210, and 8.6 mumol x min-1 x mg-1, respectively. Cellotetraose was preferentially cleaved into cellobiose (G2) plus G2, and cellopentaose was cleaved into G2 plus cellotriose (G3), while cellohexaose was cleaved into cellotetraose plus G2 and to a lesser extent G3 plus G3. G3 was not cleaved at all. G2 was the main product of Avicel hydrolysis. Xylotetraose (X4) and xylobiose (X2) were mainly produced by the enzyme hydrolysis of xylan. G2 inhibited the activity of carboxymethyl cellulase and Avicelase, whereas Mg2+ stimulated it. The enzyme was completely inactivated by Hg2+, and it was inhibited by a thiol-blocking reagent. Hydrolysis of CMC took place, with a rapid decrease in viscosity but a slow liberation of reducing sugars. On the basis of these results, it appeared that the cellulase should be regarded as endo-type cellulase, although it hydrolyzed Avicel.

Amino Acid Sequence↗
PubMed1995

Mechanical basis of ANP secretion in beating atria: atrial stroke volume and ECF translocation.

To investigate the mechanism by which an increase in pacing frequency or distension increases the secretion of atrial natriuretic peptide (ANP), the changes in atrial volume during contraction (atrial stroke volume), transmural transport of the extracellular fluid (ECF), and ANP secretion were quantified in the beating perfused rabbit atria. The atrium was stimulated by transmural field stimulation or by atrial distension induced by an increase in intraatrial pressure. Atrial stretch and incremental increases in pacing frequency up to 2 Hz activated the secretion of ANP coincident with an increase in atrial stroke volume and the transendocardial translocation of the ECF. These results showed positive relationships between changes in the secretion of ANP and the atrial stroke volume or the translocation of the ECF. The translocation of the ECF was also positively correlated with the change in atrial stroke volume. The accentuated secretion of ANP and translocation of the ECF waned at higher stimulating rates to show a peak value. Even under this condition, the secretion of ANP was a function of the translocation of the ECF. These data suggest that the increases in atrial stroke volume and translocation of ECF are fundamental factors in the ANP stimulation in response to atrial stretch and increases in atrial rate.

Animals↗
PubMed1995

A clinical study of chronic headaches: clinical characteristics and depressive trends in migraine & tension-type headaches.

BACKGROUND & OBJECTIVES: Chronic headache is commonly encountered in the neurology outpatient clinic and it is often associated with depression. In Korea, however, chronic headache has not yet been systematically investigated. We conducted this study to investigate this clinical characteristics and level of depression in patients who presented migraine, tension-type headache, or transformed migraine. METHOD: Among those with chronic headache during the period from January 1, 1994 through December 31, 1994, 131 patients were diagnosed to have either migraine, tension-type headache (by IHS classification), or transformed migraine: migraine in 60 patients, tension-type headache in 49 patients, and transformed migraine in 22 patients. Beck Depression Inventory (BDI) was performed in 116 of the 131 patients. RESULTS & CONCLUSION: There was no significant difference in the age of onset, duration of headache, and family history among the three groups. However, patients with migraine had a more severe, unilateral, and throbbing characteristic pain than those with a tension-type headache. The mean BDI scores in the transformed migraine and the tension-type headache patients were significantly higher than those of migraine, but the level of depression did not correlate with the patient's age, duration, character, severity, and frequency of headache. These findings suggest that migraine, tension-type headache and transformed migraine may be considered clinically distinct entities in viewing their different clinical characteristics and level of depression.

Adolescent↗
PubMed1995

Evolution of left atrial thrombus with anticoagulant therapy-follow-up by transesophageal echocardiography.

OBJECTIVES: Atrial fibrillation is an important risk factor for systemic embolism. A number of clinical studies demonstrated the beneficial effect of anticoagulant therapy for the prevention of embolism. But there has been no study on the fate of left atrial thrombus demonstrated by transesophageal echocardiography in the course of anticoagulation therapy. METHODS: Thirteen patients, demonstrated to have left atrial thrombus by transesophageal echocardiography were followed with anticoagulation therapy. Repeated transesophageal echocardiography was done 15 months after 1st study. RESULTS: Among 9 patients with adequate anticoagulation effect (INR > 2.0), left atrial thrombus disappeared in 3 patients. The size of thrombus decreased from 2.2 +/- 0.8cm to 0.9 +/- 1.0cm (p < 0.05 by paired Student's t-test). CONCLUSIONS: Left atrial thrombus could dissolve or decrease in size with adequate anticoagulation.

Coronary Thrombosis↗
PubMed1995

Difloxacin reverses multidrug resistance in HL-60/AR cells that overexpress the multidrug resistance-related protein (MRP) gene.

In this study, we have examined the in vitro chemosensitizing activity of difloxacin, a quinolone antimicrobial agent, in the multidrug-resistant human myeloid leukemia HL-60/AR cell line. HL-60/AR cells were found to overexpress multidrug resistance-associated protein (MRP) mRNA as compared to HL-60 cells. Difloxacin, in a concentration-dependent manner, increased the sensitivity of HL-60/AR cells to daunorubicin, adriamycin, and vincristine, and partially corrected the altered drug transport. In addition, difloxacin corrected subcellular distribution of adriamycin by inducing redistribution of the drug from the perinuclear region to the nucleus in HL-60/AR cells. The chemosensitizing effect of difloxacin was observed at clinically achievable concentrations. We conclude that difloxacin is an effective chemosensitizer of MRP-associated multidrug-resistant tumor cells and is a potential candidate for clinical use to reverse multidrug resistance.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1995

Induction of cell death by myristylated death domain of p55 TNF receptor is not abolished by Iprcg-like point mutation in death domain.

We transiently expressed the intracellular domains of p55 TNF receptor (TNFR1) as either a cytosolic- or a membrane-associated form and examined their effects on the endogenous receptor-mediated gene expression as well as on cell viability. We found that gene expression as measured by luciferase activity under NF-kappa B-controlling elements was blocked by all forms of the intracellular domain of TNFR1. The blockade of reporter gene expression was due to the cell death induced by the intracellular domain of TNFR1 per se. The killing mechanism of the intracellular domain peptides appeared to be apoptotic. Interestingly, myristylated form of the intracellular domain, consisting of mainly death domain showed the most potent cell-killing activity. Moreover, this myristylated death domain could still induce cell death even if lprcg-like point mutation (Leu351 to Ala), which has been reported to abrogate TNF-induced cytotoxicity, was introduced. This result suggests that the myristylated death domain activates an additional death signaling pathway which is not involved in TNF-induced cell death.

Apoptosis↗
PubMed1994

Allelic divergence in the human insulin gene provides evidence for intragenic recombination events in the non-coding regions: evidence for existence of new alleles.

Intragenic polymorphism of the human insulin gene (INS) was investigated in Korean subjects. The 1.9 kb INS sequence, including the 5' to 3' flanking regions, was amplified using the polymerase chain reaction (PCR), and analyzed by direct sequencing. All nucleotide sequences in the coding regions were the same as INS sequences previously reported, and four nucleotides, at positions +216, +1045, +1367, and +1380 in the non-coding regions, were found to be polymorphic. In addition to the previously identified polymorphic alleles alpha 1 (A-C-C-C) and beta 1 (T-G-T-A), new nucleotide arrangements were also identified and designated alpha 4 (A-C-C-A), alpha 5 (A-G-C-C), alpha 6 (A-C-T-C), and beta 2 (T-C-C-C). It was concluded that the new alleles may originate by intragenic recombination within INS during chromosomal crossing-over between the alpha 1 and beta 1 alleles. The allele alpha 1 was the predominant form in our sample; the new variant alleles, as well as allele beta 1, appeared to be much less frequent in INSs genes of the Korean subjects studied. Furthermore, the new alleles were detected only in heterozygous form. These results suggest that intragenic recombination can account for allelic divergence in INS.

Alleles↗
PubMed1994

Salmonella typhimurium activates human immunodeficiency virus type 1 in chronically infected promonocytic cells by inducing tumor necrosis factor-alpha production.

The effect of phagocytosis of Salmonella typhimurium on human immunodeficiency virus type 1 (HIV-1) production was investigated using a chronically infected promonocytic cell line (U1) that contains HIV-1 provirus but produces little or no HIV-1. The phagocytosis of virulent S. typhimurium by U1 cells resulted in an increased HIV-1 expression as evidenced by significant increase in HIV-1 p24 antigen in culture supernatants. In contrast, heat-killed S. typhimurium failed to induce HIV-1 expression. In addition, phagocytosis of virulent S. typhimurium and not of heat-killed S. typhimurium resulted in a significant induction of tumor necrosis factor-alpha (TNF-alpha) mRNA expression and secretion of TNF-alpha by U1 cells. Furthermore, anti-TNF-alpha monoclonal antibody inhibited S. typhimurium-induced HIV-1 p24 antigen production. These data suggest that S. typhimurium induces HIV-1 expression in U1 cells via production of TNF-alpha.

Cell Line↗
PubMed1994

Tyrosinase production in recombinant E. coli containing trp promoter and ubiquitin sequence.

We have successfully expressed the active tyrosinase of Streptomyces antibioticus in Escherichia coli under the control of the trp promoter by fusing the sequence to the ORF438 gene. Because our attempt to connect the polycistronic gene of ORF438 and tyrosinase directly to the trp promoter of E. coli resulted in the expression of functionally inactive tyrosinase, we decided to fuse the COOH-terminus of ubiquitin sequence to the NH2-terminus of ORF438. Ubiquitin fusion has been shown to augment the yield of cloned gene products in E. coli by increasing the stability or translational efficiency of the fusion proteins. As a result, E. coli transformants harboring a plasmid pTRUBF that contains the ubiquitin-fused ORF438 and the tyrosinase gene produced the strong black pigment of melanin. About 300 units of tyrosinase per liter of batch culture were detected when cultivated in M9 medium containing casamino acids, L-tyrosine, and copper supplements. The black pigment, however, was not seen when grown in LB medium, suggesting that the trp promoter is well regulated. When recombinant E. coli cells grown in LB medium were transferred to a tryptophan-deficient minimal medium with phenol, we observed that phenol was removed from the solution, and the color of the medium turned black. This is due to the fact that the tyrosinase has polyphenol oxidase properties. We expect to use this recombinant E. coli for the waste treatment of phenolic compounds.

Base Sequence↗
PubMed1994

Role of protein kinase C isozymes in activation of human immunodeficiency virus type 1 in chronically infected promonocytic cells: evidence against a role of PKC beta 1.

Protein kinase C (PKC) plays an important role in activation of human immunodeficiency virus type 1 (HIV-1). Because of a molecular and biochemical heterogeneity of PKC, we have studied the effects of PKC isozymes in HIV-1 activation in a latently infected promonocytic cell line, U1, using various PKC isozyme agonists. 12-Deoxyphorbol 13-phenylacetate (dPP), an agonist of both Ca(++)-dependent and Ca(++)-independent isozymes, and thymeleatoxin (TT), an agonist of Ca(++)-dependent PKC isozymes, induced HIV-1 production at 10 nM with increase in a concentration dependent manner, whereas 12-deoxyphorbol 13-phenylacetate 20-acetate (dPPA), an PKC beta I isozyme agonist, did not induce viral production at 100 nM. We verified that dPPA induced translocation of PKC beta isozyme with the isozyme-specific monoclonal antibody using flow cytometry. This study demonstrates that activation of PKC isozymes leads to an induction of latent HIV-1 in U1 cells whereas PKC beta I isozyme may not be important.

Cell Survival↗
PubMed1994

Quantitative study on the relation between structural and functional properties of the hearts from three different mammals.

The ultrastructural quantitative composition of left ventricular cardiac myocytes from isolated Langendorff-perfused hearts was studied in three different mammals (rabbit, guinea pig, and rat). Volume densities of mitochondria, myofibrils, and unspecified cytoplasm were determined using morphometry and were compared to functional parameters including left ventricular developed pressure (LVDP), contractility (dP/dt), heart rate, TTI (tension-time index, an index of oxygen consumption), and relative heart mass (H/B) obtained from these hearts. Each of the mammals was found to possess a very specific and characteristic quantitative composition of cardiac myocyte. Cardiac myocytes contained 26.8% mitochondria and 56.3% myofibrils in rabbits, 25.8% mitochondria and 60.9% myofibrils in guinea pigs, and 27.7% mitochondria and 58.1% myofibrils in rats. The LVDP, contractility, heart rate, and TTI were quite different among species. However, there were close correlations between the mitochondrial volume density and the LVDP (p < 0.05), and between the mitochondrial volume density and the TTI (p < 0.05), in any group of the animals. It is concluded that the mitochondrial volume density is a good indirect indicator of function of cardiac muscle related to oxidative capacity.

Animals↗
PubMed1994

Site-directed mutagenesis of tryptophan residues to conserved hydrophobic residues inhibits the processing of human KB cell folate receptor.

We are interested in identifying the ligand binding site of the human folate receptor (hFR). Previous reports have suggested a role of tryptophan(W) residues in ligand binding. We used site-directed mutagenesis to change the conserved W residues in positions 86, 116, 142, 143, 156, 160, and 193 of the hFR to either leucine(L) or phenylalanine(F) to examine the role of these W residues in hFR function. Although all W to L changes except W86L produced unstable proteins, W to F changes were tolerated. Based on total folate binding and transport studies, Chinese hamster ovary (CHO) cells transfected with W86L, W116F, and W143F expressed high levels of functional hFR, equivalent to cells transfected with wt hFR. CHO cells transfected with W142F, W156F, W160F, and W193F expressed low or undetectable levels of functional hFR although mRNA was present. Of these four mutants, only W142F expressed easily detectable immunoprecipitable protein but it was not fully glycosylated. Since glycosylation may affect the ability of hFR to bind folate, we expressed W142F in Xenopus oocytes which glycosylate the mutant and wild type proteins to the same apparent extent. In oocytes, the stoichiometry of folate binding was identical between the fully processed mutant protein and the wild type hFR. These results indicate that in CHO cells three of the seven W mutations (W86L, W116F, and W143F) function normally, whereas four of the seven W mutations (W142F, W156F, W160F, and W193F) produce unstable or abnormally processed protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1994

Effect of viscosity on oropharyngeal and esophageal emptying in man.

The effect of bolus viscosity on oropharyngeal and esophageal emptying is not known. We investigated this question in 38 healthy volunteers by measuring the transit of five semisolid boluses of varying viscosities across the oropharynx and the esophagus with the aid of scintigraphy. The studies were performed twice on consecutive days. The results show that oropharyngeal and esophageal emptying are reliably reproduced from day to day. Esophageal emptying was inversely related to bolus viscosity; however, oropharyngeal emptying was not influenced by bolus viscosity. We conclude that bolus viscosity has significant, but selective, effect on oropharyngoesophageal emptying.

Adult↗
PubMed1994

Cardiovascular effect of a naphthylmethyl substituted tetrahydroisoquinoline, YS 49, in rat and rabbit.

A novel tetrahydroisoquinoline, 1-alpha-naphthylmethyl-6,7-dihydroxy-1,2,3,4- tetrahydroisoquinoline (YS 49) 1) increased heart rate and force in isolated rat atria; 2) relaxed PE- and KCl-contracted rat aorta, and 3) decreased blood pressure and increased heart rate in anesthetized rabbit. These effects were blocked by propranolol, a nonselective beta-antagonist, but not by phentolamine, an alpha-blocker, and/or depletion of catecholamine by reserpine. These results suggest that the mechanism of action of YS 49 is due, at least in part, to beta-adrenergic receptor stimulation.

Animals↗
PubMed1994

Molecular cloning and functional expression of gicerin, a novel cell adhesion molecule that binds to neurite outgrowth factor.

Gicerin is an integral membrane glycoprotein of about 82 kd that is transiently expressed in the developing CNS. Gicerin was first identified as a binding protein for neurite outgrowth factor (NOF), a member of the laminin family of extracellular matrix proteins. By isolating and sequencing a gicerin cDNA, we have found that this protein is a novel member of the immunoglobulin superfamily. The deduced protein (584 amino acids) consists of five immunoglobulin-like loop structures in an extracellular domain, a single transmembrane region, and a short cytoplasmic tail. Cells transfected stably with gicerin cDNA adhered to NOF and aggregated with each other, indicating that gicerin exhibits both heterophilic and homophilic adhesion activities.

Amino Acid Sequence↗
PubMed1994

Determination of genome size and a preliminary physical map of an extreme alkaliphile, Micrococcus sp. Y-1, by pulsed-field gel electrophoresis.

Large restriction fragments of genomic DNA from Micrococcus sp. Y-1 were separated by pulsed-field gel electrophoresis (PFGE). Since Micrococcus sp. Y-1 has a G+C content of approximately 70%, restriction fragments were obtained by digesting chromosomal DNA with endonucleases which recognize A+T-rich sequences. Five enzymes, SspI, SpeI, XbaI, HpaI and EcoRI, were used for generation of distinctly separated fragments in the size range 100-500 kb. No site for DraI was detected. In contrast, sites for 8-base-recognizing enzymes, but not for NotI and SfiI, were frequent. The genome size of Micrococcus sp. Y-1 was determined from restriction fragments separated by PFGE, and was estimated to be approximately 4061 kb. Partial digestion experiments revealed the order of the six SspI fragments on the chromosome.

Alkalies↗
PubMed1994

Neutralization-resistant variants of infectious hematopoietic necrosis virus have altered virulence and tissue tropism.

Infectious hematopoietic necrosis virus (IHNV) is a rhabdovirus that causes an acute disease in salmon and trout. In this study, a correlation between changes in tissue tropism and specific changes in the virus genome appeared to be made by examining four IHNV neutralization-resistant variants (RB-1, RB-2, RB-3, and RB-4) that had been selected with the glycoprotein (G)-specific monoclonal antibody RB/B5. These variants were compared with the parental strain (RB-76) for their virulence and pathogenicity in rainbow trout after waterborne challenge. Variants RB-2, RB-3, and RB-4 were only slightly attenuated and showed distributions of viral antigen in the livers and hematopoietic tissues of infected fish similar to those of the parental strain. Variant RB-1, however, was highly attenuated and the tissue distribution of viral antigen in RB-1-infected fish was markedly different, with more viral antigen in brain tissue. The sequences of the G genes of all four variants and RB-76 were determined. No significant changes were found for the slightly attenuated variants, but RB-1 G had two changes at amino acids 78 and 218 that dramatically altered its predicted secondary structure. These changes are thought to be responsible for the altered tissue tropism of the virus. Thus, IHNV G, like that of rabies virus and vesicular stomatitis virus, plays an integral part in the pathogenesis of viral infection.

Animals↗